Thin-walled flexible bags are employed both in the home and industry for the packaging of a large variety of items. In the home, in particular, it is common practice to employ such bags, formed of a thermoplastic material such as polyethelyne or polyvinylchloride, for the packaging of food products which are subsequentially frozen. A more secure package is obviously obtained if a fusion seal of the open end of the thermoplastic bag could be obtained, but in the home, this is an impractical and inconvenient procedure to attempt. There is, therefore, a need for a mechanism which will effect a fusion seal of the gathered open end of a thin-walled flexible thermoplastic bag without the application of external heat.
In my Swiss Pat. application Ser. No. 4809, filed Apr. 13, 1976, I have disclosed one form of a clamping mechanism for applying substantial compressive forces to the gathered open end of a thermoplastic bag to effect the sealing thereof by cold flow of the thermoplastic material induced by the compressive forces. The clamping device disclosed in my aforementioned Swiss patent application had the disadvantage that the clamping force was applied through the advancement of a screw threaded clamping member into a threaded hole provided in the end of a mass of plastic material and at the bottom of such hole, a channel was provided for the insertion of the gathered open end of the thermoplastic bag. As mentioned in said Swiss patent application, this construction suffered from the disadvantage that only a limited amount of compressive force could be applied to the gathered bag end without the body of the clamp deforming outwardly under the effect of the compressive forces.